1. Field of the Invention
This invention relates to bonding and more particularly to an article and method for bonding a first workpiece to a second workpiece by localized heating.
2. Background of the Invention
The prior art has known various types of apparatuses and methods for bonding a first workpiece to a second workpiece. One popular method of affixing a first workpiece to a second workpiece is through the use of a brazing material. In a brazing process, a brazing material is disposed between a first and a second workpiece. When the brazing material and the first and second workpiece is elevated to a higher temperature, the brazing material liquifies to bond to the first and second workpiece. Upon solidification upon the removal of heat, the brazing material solidifies for bonding the first workpiece to the second workpiece. In general, the brazing material is a different material than the first and second workpieces thereby having a lower melting temperature. This ensures that the brazing will liquify upon the application of heat prior to any melting or liquefication of the first and second workpiece. Accordingly, the first and second workpieces are maintained intact and are not adversely affected by the application of heat.
Another type of process of bonding a first and second workpiece involves a welding process. In a welding process, a portion of a first and a second workpiece is liquified or melted with the liquified material from the first and second workpieces being allowed to co-mingle as a liquid. Upon the removal of heat, the co-mingled liquified materials are solidified thereby bonding the first workpiece to the second workpiece. The welding process has distinctive advantage over the brazing process in that the bond between the first and second workpieces are formed from the same material as the first and second workpieces. Secondly, the bond between the first and second workpieces is essentially as strong as the workpieces themselves. An unfortunate occurrence of the welding process is the deformation or partial melting or liquefication of a portion of each of the first and second workpieces.
Others in the prior art have used a sinter bond between metallic filter media and another metal component of a filter assembly. The sinter bond was produced by joining the parts through a diffusion bonding membrane. The membrane comprised a web of small diameter metal fibers which were sinter bond to both the filter media and the other filter part. Although the sinter bond provided an adequate bond between the filter media and another metal component of a filter assembly, the bond did not have sufficient strength for many operations and uses.
U.S. Pat. No. 2,642,187 to Bell discloses a replaceable filter unit of the character described comprising a pleated filter body of resin-impregnated paper arranged in tubular form and with the pleats extending substantially radially, end discs of the same material as the filter body closing off opposite ends of the body, said discs being bonded by a thermosetting resin adhesive to opposite end edges of said pleats, said adhesive lying between under faces of said discs and corresponding end edges of said pleats in contact therewith, and having turned down rims bonded adhesively by thermosetting resin adhesive to folds of the pleats, said adhesive lying between inner faces of the turned down rims and the folds of the pleats in contact therewith.
U.S. Pat. No 2,877,903 to Veres discloses a unit for filtering particulate matter from a fluid flowing therethrough, a hollow filter body comprising a screen equipped with a screen closure at one end thereof, a cap substantially closing the other end of said screen body and defining connecting means for communicating the interior of said filter body with a fluid flow line, and a mass of pellets defining a substantially continuous coating along the outer surface of the screen end closure and screen body and being bonded to each other and to the screen body and end closure to form an integrated structure therewith, whereby both said screen body and screen end closure define filtering areas through which fluid may pass to the interior of the screen body.
U.S. Pat. No. 2,957,235 to Steinberg discloses a method of assembling first and second elements composed of a mixture of powdered metal and resinous binder comprising placing said first element on a support, heating said first element until said resin binder therein becomes pliable without the element losing shape, placing said second element against said first element, applying pressure to said second element until a bond is formed by the resinous binder between said first and second elements, removing the elements from said support, cooling the assembly of said elements, supporting said assembly with sinter material in a sintering zone, and sintering said assembly into a unitary sintered structure.
U.S. Pat. No. 3,379,000 to Webber et al discloses a tow of metal filaments each having a maximum cross-section of less than approximately 10 microns and a length of approximately 50 feet and having a trace amount of a different material diffused in the outer surface thereof.
U.S. Pat. No. 3,490,902 to Fisher discloses a method for forming porous structures useful, for example, as filters, diffusion membranes, sound absorbers, and the like. The structures contain a sintered metal portion at least one surface of which having embedded and bonded thereto a reinforcing member. Some of the fibers in the fiber metal portion are bonded to each other and to the reinforcing member.
U.S. Pat. No. 3,505,038 to Luksch et al. discloses a mass comprising a plurality of randomly disposed hair-like substantially solid metal fibers, wherein said fibers are substantially free from particles of degradation and air transportable, and wherein said mass has resilient loft, substantial uniformity of density and distribution of voids, handlable green strength, and a density range of from one percent to eighty-five percent.
U.S. Pat. No. 3,716,347 to Bergstrom et al. discloses metal parts joined together with sintered powdered metal by applying a mixture of powdered metal and an organic heat-fugitive binder to the parts at the locus of the joint to be formed therebetween, assembling the parts in their desired joined configuration, and heating the assembly to volatilize or burn-off the binder and sinter the powdered metal.
U.S. Pat. No. 4,114,794 to Storms discloses an autogenous or sinter bond between metallic filter media and other metal components of a filter assembly is produced by joining the parts through a diffusion bonding membrane. The membrane comprises a web of small diameter metal fibrils which will sinter bond to both the filter media and the other filter parts to form a physically strong and leak-free seal.
U.S. Pat. No. 4,169,059 to Storms discloses an autogenous or sinter bond between metallic filter media and other metal components of a filter assembly is produced by joining the parts through a diffusion bonding membrane. The membrane comprises a web of small diameter metal fibrils which will sinter bond to both the filter media and the other filter parts to form a physically strong and leak-free seal.
U.S. Pat. No. 4,290,889 to Erickson discloses a new and unique means for preventing the crowns of a backflushable filter element unit from splitting which has heretofore been caused by the cyclic action of the cleaning and backflushing. A layer of staple material is positioned adjacent the outer layer of filter media to prevent bellowing or ballooning. An additional staple layer may be positioned adjacent the inner layer of filtered media to provide additional support. With both staple layers in position on both sides of the filter media, the media is firmly captured and the crowns will not split.
U.S. Pat. No. 4,676,843 to Nazmy discloses two component workpieces consisting of different superalloys or of the same superalloy are bonded together to form a monolithic whole, with the insertion of a layer consisting of a powder of composition similar to or identical to that of the component workpieces by hot pressing in accordance with the diffusion bonding process. The workpiece surfaces to be bonded do not have to have narrow tolerances, but are with advantage provided with grooves. The process is suitable for the bonding together of component workpieces consisting of a dispersion-hardened, nickel-based superalloy or of component workpieces of such an alloy and workpieces consisting of a cast conventional superalloy.
U.S. Pat. No. 4,875,616 to Nixdorf discloses a method for producing a high temperature, high strength bond between a ceramic shape and a metal substrate, such as joining a ceramic cap to a piston for an internal combustion engine. The composite joint is effected through the use of a ceramic preform fabricated using fibers, whiskers, platelets or sponge-like particles having the same composition as the ceramic body. The preform is joined to the ceramic shape by using a ceramic slip having a ceramic corresponding in composition with the ceramic body, with this juncture being heated to achieve a secure bond. The preform is joined to the metal substrate by first infiltrating the preform with molten material corresponding to the substrate, and then pressure bonding the infiltrated preform to the substrate after the molten material has solidified. The substrate can be metal or metal alloy. An example is given for the bonding of silicon carbide to a 300 series aluminum.
U.S. Pat. No. 5,230,760 to Tanabe discloses a filter cartridge of micro filtration membrane pleats type, by which it is possible to stably manufacture products of high quality and to reduce the manufacturing cost. In the method for manufacturing a filter cartridge of micro membrane pleats according to the present invention, an initial portion and a last portion with pleats of a micro filtration membrane are welded together to prepare an endless micro membrane, and a filter element provided with a micro filtration membrane is welded on two end plates. A thin bonding auxiliary plate made of the same material as the end plates, having an opening at its center and molten at relatively low temperature, is welded to filter element and end plates which are heated in advance.
U.S. Pat. No. 5,350,515 to Stark et al. discloses a filter cartridge including a cylindrical filter medium potted into a top cap, and having an internally potted bottom closure molded in place inside the filter medium.
U.S. Pat. No. 5,395,039 to Koehler et. al. discloses such a braze material and process. The same braze material and process is disclosed by a prior NICROBRAZ Technical Bulletin of 1991 published by the Wall Colmony Corporation regarding a braze material sold under the trademark "NICROBRAZ".
U.S. Pat. No. 5,545,323 to Koehler et al. discloses a filter assembly and a method of making a filter assembly described wherein a filter pack is seated in an end cap and contacted with a particulate material and a settling liquid of low viscosity to form a filter assemblage. The filter assemblage is sintered to form a strong, virtually impermeable bond therebetween.
It is an object of the present invention to provide an article and process for bonding a first workpiece to a second workpiece having the advantages of the brazing, welding and sinter bonding without the disadvantages of either of the processes.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece utilizing a bonding pad of the same material as the first and second workpieces.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece having a greater strength than the sinter bonding of the prior art.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece utilizing a bonding pad of the same material as the first and second workpieces wherein the bonding pad melts or liquifies prior to the melting or liquefication of a portion of the first and second workpieces.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece utilizing a bonding pad of the same material as the first and second workpieces which does not adversely flow upon liquefication of the bonding pad.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece that is capable of withstanding a cleaning solvent and an elevated temperature.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece upon the application of localized heat sufficient for transforming metallic fibers into a liquid for bonding the first workpiece to the second workpiece.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece upon the application of infrared heat between the first and second workpiece for transforming metallic fibers into a liquid for bonding the first workpiece to the second workpiece.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece upon the application of induction heat between the first and second workpiece for transforming metallic fibers into a liquid for bonding the first workpiece to the second workpiece.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece that is economical to be used in a wide variety of applications.
Another object of this invention is to provide an article and process for bonding a first workpiece to a second workpiece that provides a reliable bond for use over an extended period of time.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention with in the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention, the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.